1. Field of the Invention
The present disclosure relates to a spin device that functions by transfer of spins to a graphene. The present disclosure also relates to a driving method and a production method of the spin device.
2. Description of Related Art
Substances made of carbon (C) take a wide variety of forms including, as well as diamonds, sheets, nanotubes, horns, and balls such as C60 fullerene. Furthermore, the physical properties of such substances are more various than their forms. The rich variety of physical properties prompts energetic research and development for application of the substances. Carbon thin films are one of the substances made of carbon. Among them, a carbon thin film composed of one or several carbon atom layers in which carbon atoms are sp2-bonded is called graphene. Graphene is a substance the isolation of which was realized in 2004, and its singular physical properties as two-dimensional semimetal have been discovered one after another (Science, vol. 306, pp. 666-669 (2004)).
Graphene has a singular band structure in which two π bands having linear band dispersion intersect at the Fermi energy. For this reason, it is expected that the carrier (electrons and holes) mobility in graphene should be ten times or more the carrier mobility in silicon (Si). There is a possibility that a high-speed and low-consumption electronic device can be realized by use of graphene. In addition, graphene has an effect based on its shape with respect to the electrical conductivity. JP2009-182173A discloses that if the width of graphene in a direction perpendicular to a travel direction of carriers is reduced to several nanometers to several tens of nanometers, one-dimensional quantum confinement effect is created in a section of the graphene having such a width as indicated above, and that the graphene in this section can be used, due to the effect, as a semiconductor having an energy gap in a range of about sub-eV to several eV.
Graphene is also expected to be utilized for spin devices. This is because, in spin devices which use the spins of electrons as carriers, it is desired that spin scattering in a medium (channel) through which spins are transferred (spin current flows) should be small. Spin orbit interaction, which is a major factor of spin scattering, is dependent on the value of atomic number. Spin scattering occurring in graphene is extremely small compared with that occurring in other materials such as Si and gallium arsenide. An example of spin devices that use graphene is disclosed in Advanced Functional Materials, vol. 19, pp. 3711-3716 (2009).